1. Field of the Invention
The present invention relates to a reversible ratchet-type wrench. In particular, the present invention relates to a ratchet-type wrench that allows reversible operations without sacrificing the strength of the wrench.
2. Description of the Related Art
Wrenches are an important hand tool and have many types such as spanners, adjusting wrenches, combination wrenches, and socket wrenches. Ring spanners are very useful when the fastener to be tightened/loosened is located in a difficult-to-access place. However, the ring spanners could not be operated in a reverse direction and thus require troublesome disengagement of the ring spanner from the fastener and reengagement of the ring spanner until tightening/loosening of the fastener is achieved. U.S. Pat. No. 6,044,731 to Hsieh issued on Apr. 4, 2000 discloses a double-reversible ratchet wrench that modifies the box end of a ring spanner so as to allow reversible operation of the spanner in both directions. The ratchet wrench comprises a body, a ratchet wheel received in a receiving chamber in an end of the body, a stop block with two toothed portions mounted in the receiving chamber and meshed with the ratchet wheel to limit the direction of rotation of the ratchet wheel, a retainer ring mounted around the ratchet wheel inside the receiving chamber to hold the stop block in place, and an adjusting member mounted in the receiving chamber and turnable to shift the stop block between two positions to control the reversing direction of the ratchet wheel. However, the adjusting member would move together with the retainer ring when the stop block moves during free rotation of the wrench. Further, the adjusting member is attached to the head by a C-shaped clamp, and each of the retainer ring and the C-shaped clamp has a single function. The overall structure has increased number of elements such that the manufacture cost and the assembling time are both increased. Further, the stop block is returned to its initial position by means of cooperation between a pin and a zigzag section of the retainer ring. However, drilling a pin hole for mounting the pin would be extremely difficult for a size 8 mm wrench, and the pin hole weakens the structure of the head of the wrench. Precise processing of the pin hole is required to avoid adverse affection to the sliding and positioning of the stop block in the receiving compartment, which increases the rate of disqualified products and the manufacture cost. Further, the retainer ring and the pin still fail to provide a reliable positioning effect for the stop block; namely, the retainer ring and the pin could not reliably return the stop block to its initial position.
U.S. Pat. No. 6,220,123 to Chen issued on Apr. 24, 2001 discloses a structure of a ratchet wrench comprising a ratchet wheel mounted in a circular opening of a wrench head of a common ratchet, and a cavity is provided in the circular opening adjacent to one side of the rod body of the wrench for mounting a restrictive teeth structure. The end terminal of the cavity is provided with a ball hole to contain a spring and a steel ball, and the restrictive teeth structure is urged by the steel ball to thereby control the high-torque movement of the ratchet wheel. A rotating disc is used to cover the opening and includes ratchet teeth for meshing top ratchet teeth of the restrictive teeth structure. However, the formation of top and bottom ratchet: teeth on a side of the restrictive teeth structure would not be easy, and this decreases the torque-bearing capacity of the ratchet wrench, as the meshing area between the restrictive teeth structure and the ratchet wheel is reduced. Further, the restrictive teeth structure could not be reliably positioned, as there is no positioning means provided between the rotating disc and the wrench body. As a result, the rotating disc moves together with the restrictive teeth structure when the ratchet wrench turns freely. Further, since the top ratchet teeth of the restrictive teeth structure meshes with the ratchet teeth of the rotating disc and the bottom ratchet teeth of the rotating disc meshes with the ratchet teeth of the ratchet wheel, the ratchet wrench must be disengaged from the fastener before switching of the ratcheting direction through rotation of the rotating disc. Further, the engaging force between the ratchet wheel and the rotating disc provided by a C-shaped fastening ring was found poor. As a result, the ratchet wheel and the rotating disc could fly away from the wrench body when the ratchet wrench is subject to a relatively high torque.
It is, therefore, a need in a ratchet wrench that allows reversible operation without sacrificing the strength of the ratchet wrench and the torque-bearing capacity.
A wrench in accordance with the present invention comprises:
a handle;
a head extending from the handle and including a hole, a peripheral wall defining the hole of the head including a compartment, an annular groove being defined in an end of the peripheral wall defining the hole, the annular groove being partially coincident with the compartment;
a drive member rotatably mounted in the hole of the head and including a plurality of teeth in an outer periphery thereof;
a pawl slidably received in the compartment and including a first side having a plurality of teeth and a second side opposite to the first side, the pawl further including a first engaging member formed thereon;
a pressing member mounted in the compartment;
an elastic element mounted in the compartment for urging the pressing member to press against the second side of the pawl for engaging the teeth of the pawl with the teeth of the drive member;
a switching member having a first end mounted in the hole of the head and a second end outside the head for manual operation, the first end of the switching member including an annular groove in an outer periphery thereof, the switching member further including a second engaging member for engaging with the first engaging member of the pawl; and
a retainer ring partially engaged in the annular groove of the switching member and partially engaged in the annular groove of the head, the retainer ring being retained in place by a wall defining the compartment;
one of the switching member and the retainer ring including two retaining sections, and the other of the switching member and the retainer ring including a third engaging member for selectively engaging with one of the retaining sections;
wherein the second end of the switching member being manually turnable to make the third engaging member engage with one of the retaining sections and to move the pawl through engagement between the first engaging member and the second engaging member;
wherein the first engaging member and the second engaging member are so configured that the switching member is not moved when the pawl moves as a result of free rotation of the wrench.